docs: def deleteAttachment(self, oid, attachment_id):
          """ removes an attachment from a feature service feature
              Input:
                oid - integer or string - id of feature
                attachment_id - integer - id of attachment to erase
              Output:
                 JSON response
          """
          url = self._url + "/%s/deleteAttachments" % oid
          params = {
              "f":"json",
              "attachmentIds" : "%s" % attachment_id
          }
          return self._post(url, params,
                               securityHandler=self._securityHandler,
                               proxy_port=self._proxy_port,
                               proxy_url=self._proxy_url)